Hello!
The pins on W_PUMP are the same as the pins on a fan header. As long as the fan's power usage is within limits for the plug, you should be ok using the W_PUMP connector for a fan. The speed of the W_PUMP connector should be based on CPU temperature, so keep that in mind for usage on a case fan.
Within your BIOS there is a section for you to choose if you want W_PUMP connector to use PWM control, DC, or have it automatically switch between control mode depending on what is connected.